The document consists of 400 pages on each page there are 3200 characters each character takes 8 bits.

The document consists of 400 pages on each page there are 3200 characters each character takes 8 bits. The question is how many kilobytes is the text.

400 * 3200 * 8 = 10240000 bits = 1280000 bytes = 1250Kbytes
To find how much text takes up, you need to multiply the number of pages by the number of characters on the page and the amount of space occupied. Then we translate from bits to KB. First we divide by 8 (from bits to bytes), then we divide by 1024 (from bytes to KB).